Add alternate comparison types to versions

- The types are:
-- Previous: The default and the previously used type
-- Subsequent: Compares against the next version
-- Current: Compares against the current version
- Allow switching between comparison types in index and diff views
-- Have links vary depending upon current comparison type

app/views/wiki_page_versions/_listing.html.erb

@@ -2,7 +2,7 @@
   <%= form_tag(diff_wiki_page_versions_path, :method => :get) do %>
     <%= table_for @wiki_page_versions.includes(:updater, :tag), width: "100%" do |t| %>
       <% t.column column: "diff", width: "3%" do |wiki_page_version, i| %>
-        <%= link_to_if wiki_version_show_diff(wiki_page_version), "diff", diff_wiki_page_versions_path(otherpage: wiki_page_version.previous.try(:id), thispage: wiki_page_version.id) %>
+        <%= link_to_if wiki_version_show_diff(wiki_page_version, params[:type]), "diff", diff_wiki_page_versions_path(thispage: wiki_page_version.id, type: params[:type]) %>
       <% end %>
 
       <% if listing_type(:wiki_page_id, member_check: false, types: [:page, :global]) == :page %>
@@ -20,10 +20,10 @@
           <%= link_to wiki_page_version.title, wiki_page_version %>
           <%= link_to "»", wiki_page_versions_path(search: { wiki_page_id: wiki_page_version.wiki_page_id }) %>
         </span>
-        <%= wiki_version_title_diff(wiki_page_version) %>
+        <%= wiki_version_title_diff(wiki_page_version, params[:type]) %>
       <% end %>
       <% t.column "Changes", width: "5%" do |wiki_page_version| %>
-        <%= status_diff_html(wiki_page_version) %>
+        <%= status_diff_html(wiki_page_version, params[:type]) %>
       <% end %>
       <% t.column "Updated", width: "26%" do |wiki_page_version| %>
         <%= compact_time(wiki_page_version.updated_at) %>

app/views/wiki_page_versions/diff.html.erb

@@ -4,21 +4,33 @@
 <%= render "wiki_pages/sidebar" %>
 
 <% content_for(:content) do %>
-  <h1>Wiki Page Version Comparison:  <%= link_to @thispage.title, wiki_page_versions_path(search: { wiki_page_id: @thispage.wiki_page_id }, anchor: "wiki-page-version-#{@thispage.id}"), class: "tag-type-#{@thispage.wiki_page.category_name}" %></h1>
+  <h1>Wiki Page Version Comparison:  <%= link_to @thispage.title, wiki_page_versions_path(search: { wiki_page_id: @thispage.wiki_page_id }, type: params[:type], anchor: "wiki-page-version-#{@thispage.id}"), class: "tag-type-#{@thispage.wiki_page.category_name}" %></h1>
 
-  <p>Showing differences between <%= compact_time @thispage.updated_at %> (<%= link_to_user @thispage.updater %>) and <%= compact_time @otherpage.updated_at %> (<%= link_to_user @otherpage.updater %>)</p>
-
-  <% if wiki_version_show_other_names(@thispage, @otherpage) %>
-    <p><%= wiki_version_other_names_diff(@thispage, @otherpage) %></p>
-  <% else %>
-    <p><em>No changes to other names.</em></p>
+  <% if params[:type].present? %>
+    <%= render "versions/types" %>
   <% end %>
 
-  <% if @thispage.body != @otherpage.body %>
-    <div class="diff-body">
-      <%= diff_body_html(@thispage, @otherpage, :body) %>
-    </div>
+  <% if @otherpage.present? %>
+    <% if @thispage.id != @otherpage.id %>
+      <p>Showing differences between <%= compact_time @thispage.updated_at %> (<%= link_to_user @thispage.updater %>) and <%= compact_time @otherpage.updated_at %> (<%= link_to_user @otherpage.updater %>)</p>
+
+      <% if wiki_version_show_other_names(@thispage, @otherpage) %>
+        <p><%= wiki_version_other_names_diff(@thispage, @otherpage) %></p>
+      <% else %>
+        <p><em>No changes to other names.</em></p>
+      <% end %>
+
+      <% if @thispage.body != @otherpage.body %>
+        <div class="diff-body">
+          <%= diff_body_html(@thispage, @otherpage, :body) %>
+        </div>
+      <% else %>
+        <p><em>No changes to body.</em></p>
+      <% end %>
+    <% else %>
+      <p><em>Version is latest!</em></p>
+    <% end %>
   <% else %>
-    <p><em>No changes to body.</em></p>
+    <p><em>No versions to compare!</em></p>
   <% end %>
 <% end %>

app/views/wiki_page_versions/index.html.erb

@@ -3,6 +3,8 @@
 <% content_for(:content) do %>
   <h1>Wiki Page History</h1>
 
+  <%= render "versions/types" %>
+
   <%= render "listing" %>
 
   <%= numbered_paginator(@wiki_page_versions) %>